Blast hole drills are large but mobile machines used primarily in surface mining to drill holes for explosives. They are mounted on crawlers to provide mobility but are provided with hydraulic jacks to raise and support the machine off the crawlers during drilling operations. It is important that the machine be level for drilling to assure that the drill hole will be at the desired angle or vertical. It is also important that the raising or lowering procedure be conducted with the platform as level as possible so as to reduce frame stress. Further, the time required to perform a raising or lowering procedure should be maintained at a minimum.
Various types of raising and leveling systems for blast hole drills have been provided in the past. In some instances the entire leveling operation was controlled manually. One type of automatic leveling system for blast hole drills is described in U.S. Pat. No. 3,625,483 which is assigned to the assignee of this invention. In that particular leveling system, proportioning valves were utilized in conjunction with two level sensors for monitoring the raising and lowering of the main frame of a blast hole drill. In U.S. Pat. No. 4,453,725 a road vehicle level controller is described wherein a microcomputer is used in conjunction with a five level detector operation.
The prior art does not provide an automatic leveling system for large and heavy industrial equipment wherein the raising or lowering procedure can be stopped when the deck of the equipment is out of level by more than a predetermined degree and which can re-level the deck within a prescribed degree. The prior art is mainly concerned with continuous type leveling systems for blast hole drills or with maintaining vehicles at predetermined levels based upon weight loads.
It is an advantage of the present invention to provide an automatic leveling system for blast hole drills or the like which can automatically monitor the machine within a predetermined degree of level during raising or lowering.
It is another advantage of this invention to provide leveling system of the foregoing type which is especially suitable for being controlled by a programmable controller.
It is yet another object of this invention to provide an automatic leveling system for a blast hole drill which reduces main frame stress during raising or lowering, increases hole pattern accuracy and reduces the amount of operator interface. Other features and advantages of the invention will become apparent as well as a better understanding of the invention from the descriptions following.